We propose collaborative studies of glycan modulation of inflammatory responses involving myeloid cells, endothelial biology, innate immunity and host-microbial interactions - using genetically-modified mice and bacteria. A particular focus is on roles of two major types of anionic glycans: sialic acids (Sias) and the glycosaminoglycans (GAGs), hyaluronan (HA), heparan sulfate (HS) and chondroitin sulfate/dermatan sulfate (CS/DS). Specific glycan-binding proteins differentially recognize these glycans, mediating many important functions in inflammation. Many physiologic and pathological roles of such glycans are not fully evident in cultured cells, and some such as roles in inflammation must be explored in an intact vertebrate. An underlying theme of this PEG is state-of-the-art genetic manipulation of these glycans, and/or their cognate binding proteins in the mouse. Our highly interactive team of experts is support by state-of-the-art Core facilities with many opportunities for intellectual and practical collaborations and synergies. Project 1 will elucidate functions of activatory and Arg-mutated forms of CD33-related Siglecs on myeloid cells, which likely represent evolutionary adjustments to pathogens expressing Sias. Project 2 will study innate immune functions of myeloid cells challenged by microbes that either mimic host Sias or GAGs, or which produce glycosidases targeting them. Project 3 studies sulfation patterns of HS and CS/DS chains in regulating myeloid cells and endothelial biology. Project 4 investigates how HA catabolism acts during inflammation to modulate the innate immune response. We proposed five cores to support the research and training objectives ofthe PEG: Core A, a Glycosciences Skills Development Core for recruitment and training of Fellows;Core B, a shared resource for Glycan Synthesis and Analysis;Core C, Administrative and Mouse Management Core;Core D, Histopathology;and Core E, Hematology and Clinical Chemistry. The overall objective is to understand the multi-faceted roles of Sias and GAGs in the biology of inflammation, enhance resources for glycosciences, and to identify and train the best postdoctoral fellows who have a strong potential to develop into an outstanding independent investigators working in areas relevant to NHLBI.